/**
     * Refill Tracker - Shows which shops have been refilled and which haven't
     */
    public function refillTracker($agentId)
    {
        $agent = Agent::findOrFail($agentId);
        
        // Get past 2 weeks date range
        $twoWeeksAgo = Carbon::now()->subWeeks(2);
        
        // Get all agent's shops
        $shops = Shop::where('agent_id', $agentId)->get();
        
        // For each shop, get refills from past 2 weeks
        $shopsData = $shops->map(function($shop) use ($twoWeeksAgo) {
            $refills = RefillRequest::where('shop_id', $shop->id)
                ->where('status', 'approved')
                ->where('request_date', '>=', $twoWeeksAgo)
                ->with('product')
                ->orderBy('request_date', 'desc')
                ->get();
            
            return [
                'shop' => $shop,
                'refills' => $refills,
                'total_refilled' => $refills->sum('quantity_approved')
            ];
        });
        
        // Calculate summary
        $shopsWithRefills = $shopsData->filter(function($data) {
            return $data['refills']->count() > 0;
        })->count();
        
        $shopsWithoutRefills = $shopsData->filter(function($data) {
            return $data['refills']->count() === 0;
        })->count();
        
        $totalUnitsRefilled = $shopsData->sum('total_refilled');
        
        return view('agent.sales.refill-tracker', compact(
            'agent',
            'shopsData',
            'shopsWithRefills',
            'shopsWithoutRefills',
            'totalUnitsRefilled'
        ));
    }